U.S. Pat. No. 5,699,255 discloses an apparatus and method for providing map information of varying resolution to a navigation device. In one embodiment, a position determining system is attached to the navigation device. The position information is transmitted to a base station containing map information. Map information related to the location of the navigation device is then transmitted from the base station to the navigation device using a bidirectional communication link. The base station only transmits map information related to the position information of the navigation device.
A drawback of this method is that it uses a substantial amount of resources if a substantial amount of navigation devices is present, as these would all require a dedicated data stream from and/or to a base station.